Mobile animals orient to salient features of their environment. In some animals, such as primates, covert orienting of attention has evolved as a flexible mechanism for monitoring potentially important locations or stimuli in the absence of overt orienting. Psychophysical and neurophysiological studies conducted in the laboratory have extensively probed these attentional mechanisms in primates trained to discriminate simple stimuli whose salience or behavioral significance is arbitrarily assigned. Observational studies of primates conducted in field settings, however, suggest that particular stimuli, such as visual images of conspecifics, are intrinsically salient and elicit overt orienting of attention. It remains unknown whether these stimuli also evoke covert shifts of attention under naturalistic behavioral conditions, although these are presumably the ecological conditions in which covert attentional mechanisms evolved. Just how the attentional mechanisms so extensively studied by psychologists and neuro-biologists function in animals performing naturalistic behaviors, which do not require extensive training, remains obscure. These lacunae suggest that a unified approach combining ethological, psychological, and neurobiological techniques would provide a powerful new paradigm for understanding mechanisms of attention in both human and non-human primates. The goal of the proposed research project is to develop a neuro-ethology of primate attention. Psychophysical techniques will be used to quantify the intrinsic salience or motivational value of visual images of familiar conspecifics for both covert and overt orienting of attention in particular behavioral contexts. Concurrently, neurophysiological techniques will be used to study the representation of the intrinsic motivational salience of socially meaningful images in parietal cortex, an area of the brain known to play a critical role in both overt and covert orienting of attention. The synergistic approach developed in this proposal offers the promise of an integrated neuroethology that may reveal unique insights into the evolution of attentional mechanisms in primates, including humans.